(under subclass 28) Counting and cancelling mechanism, usually of the step-by-step variety, is provided, whereby as many trains or car-wheels as enter must leave the block before the signal can be restored to safety.
SEE OR SEARCH THIS CLASS, SUBCLASS:
19, 72, 81, and 247, for systems using propulsion-current, but lacking counting and canceling devices.
19, 78+ and 247, for counting mechanism.
246+, and subclasses mentioned in the search notes appended thereto, for various types of circuit-controllers.
